David Gius, M.D., Ph.D.

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Sirtuin 3 A Mitochondrial Watchdog Protein
David Gius, M.D., Ph.D. Professor, Departments of
Cancer Biology, Pediatrics, and Radiation
Oncology Vanderbilt University School of Medicine
Vanderbilt Medical School
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The Human Sirtuins

• Nuclear
• Sirt1
• Sirt6
• Sirt7

• Mitochondrial
• Sirt3
• Sirt4
• Sirt5

• Cytoplasmic
• Sirt2

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Protein Deacetylation as a Post-Translation
Protein Modification
Non-Histone Protein
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Rational for Sirtuins as Tumor Suppressors
Carcinogenesis
Decreases aging
Increasing age
Caloric Restriction
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Tumor Suppressor Gene

• Loss of function results in an in vitro tumor
  permissive cellular phenotype (two hit tissue
  culture immortalization.
• Genetic knockout in mice results in the formation
  of murine tumors.
• There is a loss of function or decrease in
  protein levels in human malignancies and this
  matches human samples.

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Two Gene Transformation Model for MEFs
TSG Gene Loss
Myc
Ras
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Sirt3-/- MEFs are immortalized by a Single
Oncogene
Sirt3/ Myc/Ras cells Sirt3-/- Myc/Ras cells
Kim et al, 2010 Cancer Cell
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In Vitro Transformation Sirt3-/- MEFs by a
Single Oncogene
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Mammary Carcinogenesis in the Sirt3 knockout mice
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SIRT3 is Decreased in Human Breast Cancers
Tissue Array (IHC)
RNA Array (RT-PCR)
Kim et al, 2010 Cancer Cell
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SIRT3 is Decreased in Human Breast Cancers
Oncomine, UMich
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Sirt3 is a mitochondrial tumor suppressor but

• Mechanism?
• Is it a sensing protein?
• What are the targets of Sirt3 ?
• Or what dysregulated proteins play a role in the
  Sirt3-/- tumor permissive?

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Transformed Sirt3 KO MEFs exhibit mt Superoxide
Kim et al, 2010 Cancer Cell
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Primary Mitochondrial O2- Detoxification Pathway
O2-
H2O2
H2O O2
MnSOD
Catalase
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Criteria for Potential Sirt3 physiological Target

• A protein that contain at least one reversible
  acetyl lysine that is altered by either caloric
  restriction, feasting, or other type of stress.
• A Protein is hyperacetylated in the Sirt3
  knockout livers or MEFs.
• A protein contains at least one lysine that is
  deacetylated by Sirt3 both in vitro and in vivo.
• The reversible acetyl lysine is evolutionary
  through out multiple species including less
  complex species.
• Acetylation of the target lysine regulates
  enzymatic activity.

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MnSOD contains a reversible lysine
Tao et al., 2010, Molecular Cell
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MnSODs reversible is deacetylated by Sirt3
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MnSOD K122 is an evolutionarily conserved
reversible lysine
Tao et al., 2010, Molecular Cell
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MnSOD K122 is Deacetylated by Sirt3 in vitro and
in vivo
In vitro
In vivo
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(No Transcript)
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MnSODK122 acetylation status directs dismutase
activity
MnSOD-/- MEFs
Tao et al., 2010, Molecular Cell
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MnSODK122-R prevents in vitro Immortalization
Tao et al., 2010, Molecular Cell
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MnSOD De-Acetylation Responds to Exercise and CR
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O2-
O2-
O2-
-

O2-
O2-
H2O2
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How does MnSOD fit into this model??
Fasting Metabolic State
Feasting Metabolic State
ATP and Oxidative damage
Repair of Oxidative damage
MnSOD
AC
AC
AC
AC
AC
AC
AC
AC
Longevity Hibernation Energy Conservation
Aging Cancer Pro-metabolism
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The Gius Lab